Microsoft Real-time Compression Interface (MRCI)

 Microsoft Real-Time Compression Interface (MRCI; pronounced "mercy")
 provides a means for application programs and system utilities to compress
 and decompress data.

 It is normally installed as part of DBLSPACE.BIN file which is loaded at
 boot time (see DoubleSpace Overview), but it may exist as ROM-based,
 hardware-assisted server installed via ROM-Scan at system powerup.

     See: INT 2fH 4a12H (see if MRCI is installed; get entry addr, etc.)
          INT 1aH b001H (check for ROM-based MRCI server)

          MRCI Fn 0001H (compress data)
          MRCI Fn 0002H (decompress data)
          MRCI Fn 0020H (incrementally decompress data)
          MRCI Fn ffffH (deinstall server; not used)

          MRCI API Error/Return Codes (codes returned by these fns)

          MRCInfoRec structure
          MRCRequestRec structure

   Notes: ■ In order to use MRCI fns, you must obtain the API entry address
            (and a MRCInfoRec used in every call) via INT 2fH 4a12H.

          ■ The decompression services require knowledge of the original
            (uncompressed) size of the data.

          ■ Pragmatically, the uses of these fns are limited.  Since you
            can assume that a disk compression system such as DoubleSpace
            is installed, there is no reason to compress data for storage
            on a local hard disk.

            You might want to use MRCI for storing backup data to diskette
            or perhaps for sending data across a network (or other
            bandwidth bottleneck, such as a modem line).  Msbackup uses
            MRCI fns to compress backup data.

          ■ One novel idea is to use MRCI to compress screen data for
            temporary storage in RAM.  For instance, a 4K text-mode screen
            typically compresses to a few hundred bytes.

See Also: DoubleSpace Overview
          DoubleSpace API
          DOS Functions